Understanding Alzheimer disease

The brains of Alzheimer disease patients have two unusual hallmarks: plaques and tangles. The tangles are accumulations of an altered form of a normal brain protein, tau, which clogs neurones, eventually killing them. Plaques are accumulations of an altered form of another brain protein, -amyloid, outside the brain cells. Scientists do not yet know why the altered -amyloid builds up in the brains of some people but not in others, as they age.